After testing, I can say that LimeSDR-Mini works very well with Orange Pi Zero and osmocom gsm stack. With 5000 mAh powerbank and cooling fan it takes the place of 13x7x5 cm in the cardboard box from the smartphone and 13x7x4 cm without.
Its just a prototype, and I think it may be smaller.
More about how hardware and software turned together: https://codeby.net/threads/miniatjurnaja-sotovaja-stancija-na-baze-limesdr-mini-i-orange-pi-zero.66747/
Configs for lime mini, orange pi zero and osmo-nitb: https://github.com/DrLafa/osmo-nitb-scripts